A defibrillator is a therapeutic instrument that is useful in curing certain cardiac irregularities, particular ventricular fibrillation and atrial fibrillation. The defibrillator typically includes a pair of large paddle electrodes, and operates to apply a high energy DC pulse to a patient through the paddle electrodes when appropriately triggered by an operator. The paddle electrodes are held in the operator's hands when the defibrillation pulse is administered. In one common technique (anterior/anterior), one paddle electrode is placed lateral to the upper sternum and below the right clavicle on the patient's right chest, and the second paddle electrode is placed on the patient's lower left chest, usually just below and lateral to the cardiac apex. In a second known arrangement (anterior/posterior), the anterior paddle electrode is placed over the precordium, and the posterior paddle electrode is placed on the patient's back behind the heart. Since a patient will usually be unconscious and lying on his or her back, the size of a paddle electrode and the requirement that it be held by the operator generally make the anterior/posterior technique impractical when only paddle electrodes are available.
Other well known types of defibrillator electrodes include internal electrodes and low-profile disposable electrodes. Internal electrodes are small electrodes that are used during surgery when the heat is exposed, and are applied directly to the heart. Disposable electrodes are flat, low-profile electrodes that include adhesive so that the electrode can be secured to a patient's skin. Unlike a paddle electrode, a disposable electrode can be applied to a patient's back, permitting the use of the somewhat more efficient anterior/posterior defibrillation technique. The use of disposable electrodes also permits the electrodes to remain attached to a patient while the patient is moved, e.g., while the patient is moved from an ambulance into an emergency room, thereby permitting a faster response should defibrillation subsequently be needed.
In the past, defibrillators have accommodated different types of electrodes by providing a set of external connectors to which the different electrodes could be electrically connected. The disadvantage of such an arrangement is that the paddle electrodes are not always available for use. Furthermore, such an arrangement gives rise to the possibility that the defibrillator will be left in a state in which no electrodes are attached or available.